Its foraged Nordic ants, live shrimp and locally sourced carrots in malt soil have seen it voted the best restaurant in the world three times over; its tasting menu costs £170 a head, or almost double that with wine – that's if you can get a table.

But, given its cult following, even the three-month wait for a reservation at Noma in Copenhagen is unlikely to shorten despite more than 60 diners falling ill due to a vomiting and diarrhoea bug after eating there.

In the meticulous and cut-throat world of international super-restaurants, it was a surprise that Noma's award-winning designer kitchen had spread viral gastroenteritis to scores of customers last month.

The Danish food authority report came days before the Michelin Guide was due to unveil its latest star ratings for Copenhagen next Thursday, with hopes pinned on the two-starred Noma to finally win three stars after years of speculation that its modern Nordic dishes such as poached sea urchin and powdered cucumber deserved the top accolade. Noma has replaced Catalonia's El Bulli as the focus of rapture for international food critics.

Health inspectors criticised the restaurant for not alerting authorities soon enough and for not taking proper action after an employee fell ill upon returning home after work. In total, 63 customers who had eaten there between 12 and 16 February said they were sick. It was not immediately clear what food had caused the infection.

The authority downgraded their "smiley" food safety rating from an ear-to-ear grin to a more lukewarm smile and criticised the restaurant for having no hot water in the tap at one of the kitchen sinks.

In a statement Peter Kreiner, Noma's managing director, told Danish newspapers: "It is a matter that affects us all deeply, and which we are really sorry about."

The restaurant recognised that internal procedures had not been good enough and said an email from the employee reporting the sickness had not been seen.

He also said the faulty tap had been fixed by a plumber straight after the inspection and that the restaurant had changed its procedure around staff emails to avoid any future delays.

Kreiner said the restaurant was co-operating with health authorities and organising customer compensation.

One pregnant diner, Line Karlsson, 30, from Copenhagen, told the Danish paper Politiken she had lunch at Noma with her boyfriend on Valentine's Day.

"It was nice and delicious," she said. The next day her boyfriend fell ill with vomiting, diarrhoea and fever although Karlsson wasn't hit as badly.

"When we went back to work, people asked if it could have been because of the food at Noma, and we said no, it couldn't possibly be that." But after reading about the incident, she realised it "fitted together". Asked if she would return if she was offered another meal, she said: "Yes, please. You expect that this is an isolated case."

Noma has been three times voted world's top restaurant in San Pellegrino World's 50 Best Restaurants list. Its head chef Rene Redzepi was named as one of Time magazine's most influential people last year, dubbed a "locavore hero" who has influenced a craze for strict seasonality, regional ingredients and local cooking.

A spokeswoman from the Michelin guide to Copenhagen, said: "The guide and ratings for 2013 have already been set" and there would be no changes because of the incident.

In 2009, Heston Blumenthal's Michelin-starred Fat Duck restaurant in Bray, Berkshire saw the biggest commercial restaurant food poisoning outbreak ever recorded with at least 240 people falling sick with gastroenteritis. Contaminated oysters and handling of food by infected staff were said to be the likely causes. Blumenthal apologised and demand for tables did not diminish.